The use of aerial photography in surveillance applications is well known. Typically, an aircraft flies over the desired area and photographs the ground utilizing equipment and techniques which tend to optimize the resolution of the resulting photographs. Such optimization of the resolution of the photographs is typically desirable so as to enhance the photointerpreters ability to accurately and reliably determine the content of the photographs.
However, in some instances, it is desirable to limit the resolution of the photographs obtained from aerial photography and the like. One instance where such resolution limitation is desirable is when such aerial photography is being performed according to a treaty which specifies the maximum, i.e., best, resolution, with which such photographs may be taken. For example, the Open Skies Treaty limits the ground resolution of aerial photography performed according thereto to 30 cm.
Thus, in order to comply with such a treaty, or so as to otherwise limit the resolution of a camera or other optical instrument, it is desirable to provide means for blurring photographs which is low cost, easy to use, and verifiable according to the terms of the treaty, if any.
It is further desirable that such means for limiting the resolution of pictures not require the blurring process take place after an original image is created. The reason is that the original must be disposed of in a secure manner. Those skilled in the art will appreciate that if the original image is formed at full resolution and after that a second image is generated therefrom at the desired resolution, such procedure makes it possible for some people to have access to the original, full resolution image. Thus, it is desirable to provide means for limiting the resolution of a camera such that only a degraded, i.e. resolution limited, image is formed.
It is further desirable that any such resulting resolution limited image not be capable of digital resolution enhancement. Thus, the image must be degraded in a manner which introduces substantially random noise so as to avoid subsequent reconstruction of an imaging having greater resolution than that of the original blurred image.